Previously, only "selected chapters" were shown in left-pane ToC (of
Read The Docs theme). These chapters were selected out of order. The
rest of chapters were hidden beyond "Documentation Contents" pseudo-
chapter. This arguably led only to confusion, as many people probably
never tried to open that pseudo-chapter, and those who did, were
confused. Such organization is even worse for PDF output, causing
chapters go in mix-mashed order.
So, instead move to single clean ToC. This will allow readers of HTML
to have access to any doc content at their fingertips (and straight
before their eyes), and will allow to finally have clean PDF docs.
